Apparatus for machining spiral grooves



R. A. THOMPSON 2,354,411

APPARATUS FOR MACHINING SPIRAL GROOVES July 25, 1944.

Filed Dec. 50, 1937 3 Sheets-Sheet l INVENTOR.

fwd. ATTORNEY5.

y 1944- Y R. A. THOMPSON 2,354,411 I APPARATUS FOR MACHINING SPIRAL GROOVES Fi led Dg c. 30, 1937 3 Sheets-Sheet 3 12v VENTOR F 12%d 'd l1 Tam vsalz. BY

Patented July 25, 1944 APPARATUS FOR. monmmcgsrntei; "i v fGROOVES Richard A. '.l;l 1ompson,: Detroit,. Mich;, assignor to Colonial Broach. Company, Detroit, Mich., a

corporation of Delaware 'ApplicationiDecem'be'r 30, 1937, SerialNo. 182,549 V My invention relates tobroaching machines; and, particularly to a machine for accurately breaching spiral grooves in a work piece to "provide lands therebetween. Y My invention pertainsparticularly to a means for broaching spiral grooves in a gun barrel'to provide spiral lands and grooves therein which are accurately shaped and spaced from each other throughout the length of the barrel; When machining grooves in gun barrels heretofore, it has been the practice to employ a single tool which operated to machine a single TOovejn the gun barrel each passage of the tool therethrough. The tool was indexed aseach slot was cut therein and difiiculty was always experienced in obtaining uniform widths and spacing'of the lands throughout the length of thebarrel. Such;

uniform disposition of the lands is essential in gun barrels in view of the fact thatan impression of the land and groove is madein the pro? jectile immediately upon'its entrance into the barrel and which entirely fills the "grooves'fof the barrel to form a gas seal therewith. If at any point throughout the length of th barrel the width and spacing of the lands andgrooves vary, the projectile will be distortedand the gas would leak past the deformed portion. I

In practicing my present invention, I provide abroach having accurately disposedvspiral rows of teeth of predetermined width and varying spacing and width with grooves machined. in.

similar gun barrels. This uniformity is tobe'de sired andris readily obtained when employing my broaching tool. The faces of the teethfare disposed on a helical lead at right angles to the lead. of the rows of teeth so that similarcutting'edges will be provided on either side of the; teethfacesl The broach is short in length and preferably has I provided, on its front end means for preventing its insertion in the receiving chamberande its rear end, a socket for receiving theend of apush rod to form a ball and socket connection therewith which permits the turning ofthe .broach independentof the push rod. 1 a

The machine for. effecting the breaching oper; ation has a bed provided with a reciprocablehead engaging a push rod which is guided upon ap airl of bars which pass through the'head and which are accurately alignedwith the breach receiving chamber. The end of, the push rodis sealed into thechamber, preferably by a packing gland; and is accurately aligned with the aperture in the gun barrel. The gun barrel is preferably mounted on the broach receiving'cham'ber in the same mannerthat it is secured to the gun receiver while the front end ispreferably accuratelysup ported-aligned with-the push rod by a coneshaped clamp which engages thefront peripheral edge of the-barrel. The broa'ching chamber is provided with anorifice into whicha coolant such as" soda? oil and the like, is'introduced under'jpressure Th coolant under pressure is forced about the broach through-thegun barrel to break oifjthej fine chips and carry them from the barreL- suitable deflector is provided beyond'th'e froni i clamp which deflects the coolant into I a reservoir provided in'the 'baseof the machine. The broaciif having-t'eeth with like cutting'edges on both sides and having "a slow lead; thatis to say, having af helical lead of small angle, will be turned by the teeth as it is being ipushed through the gun bar; rel by the pushrod in the presenceof the ball and socketconnection therebetween @cpordingly, 'the main objects of my. invention, are to provide albroachior' machining accurat grooves in gunjbarrelsor like articles; tojprovi f aimachine with a' guided, push rod ,for forcing a; separate broach through a tubularelement; tg'i sear-epu nrod in a'charnber for receiving the; broach and, for supportingva tubular Work e1eZ' nient, in alignment Withthe. broach. andpush' rod; to deliver a coolant under pressure, to. a breach receiving chamber which flows lover and aheadfof, the broach andbreaks off and washes chips from thework. piece; to provide-a conned; tion betwe en thellpush rod. and. breach. which permits the L broach to freely-I turn, independent ofthe push. rod; to provide means. on the front endof' thebroach to prevent the front end from; being i n sert i =.d in. the broach receiving chamber}: aridfin .general,1jto provide a broach, apparatus and means for accurately machining grooves in; avtubular element which issimple in .construc: tion, positive in,operation, .and economical of manufacture.

T Other objects and features. of novelty of invention will be specifically-pointed out-or will become apparent, .when referring .forabettehun derstanding of my: invention to the followingdei rip ionl taken-insconjunetion with the accompanyingdrawingswhereint Figure 1. is a broken. yiew,. inlelevation; of broaching machinejernbo'dying, features of my invention; .l a Y Fig. 2 is an enl'arged sectional: viewof the; structure illustratedin Eigl taken [on the line 2-2 thereofz' Fig. 3 is a broken sectional view of the structure illustrated in Figure 2, taken on the line 3-3 thereof;

Fig. 4 is an enlarged sectional view of the structure illustrated in Fig. 3, taken on the line 44 thereof;

Fig. 5 is an enlarged sectional view of the broach receivingchamber illustrated in Fig. '1;

Fig. 6 is an enlarged broken view, with parts in section, of the broach illustrated in the broach receiving chamber of Fig. 5;

Fig. 7 is a sectional view of the structure illustrated in Fig. 5, taken on the line 'l-I thereof};

Fig. 8 is a sectional view of the structure illustrated in Fig. 6, taken on the line 8--8'th ereof,l

and

Fig. 9 is a section of the finished barrel taken normal to its axis. Fig. 10 is a side elevational view, partly in crosssection, of a machine constructed according to rod l3 secured-to a piston head l4 operating in a hydrauliccylinder [5. The head I2 is recip rocated through the operation of the piston. in the cylinder in a well known manner and will not be further described. Other means besides the hydraulic mechanism may be employed for operating the head,l2 such as a lead :screw, a rack and pinion or other well known device capa-v ble of producing a motion in reciprocation.

A pairof g'uidefbarslfi are supported onthe bed, the right-hand ends, as viewed in Fig. 1 being supported on uprights I! while the left ends are supported by the projections l8 on the chamber casting IS. The guide bars l6 are accurately located in the head l2 on guide elements 2| which have bearing engagement with the top, bottom and, outer sides of the guide bars.

The guide barsf it are provided on their inner face with projecting tongues 22, the. inner surface of which are accurately shaped to engage a push rod 23. The push rod is integral with an element 24 whichv is secured to the head l2 and which slides between the tongues 22 of the guide bars I6. During the movement. of the head l2, any sag in the bars will be taken up by the guide elements 2| .so as to retain. them accurately aligned in position when supporting the push rod 23 as it is being moved forwardly or backwardly bytheheadl2.

The push rod23, projects into the chamber 25 of the chamber casting I9 and leakage of fluid around the rod is preventedby a packing gland 26 which is retainedin position by a clamping element 21. j The chamber supports a broach receiving tube 28'having one end disposed in a bushing 29 accurately aligned with the end of the push rod 23. The opposite endof the tube issupported by a collar 3| which is screwed into the threads provided on the inner surface of the chamber 25. A suitable packing element 30 may be employed to effectively seal the collar to the broach receivingtube 28.

A work supporting cap 32 is also ecured by 7;

the threads in the inner wall of the chamber 25 and is provided with a central aperture 33 aligned with the broach receiving element 28. The central aperture 33 is shaped and machined to re- 5 ceive the end of the gun barrel in the same manner that it is held by the receiver. In this manner, the barrel is supported exactly aligned with the broach receiving element 28 and the broach v The opposite end of the barrel is supported by an engaging element 34 having a conical end w hich engages the peripheral end of the barrel. The element 34 is mounted in a head 35 for v movement in reciprocation toward and away from the barrel produced by a pinion 36 operated by a wheel 38 to rotate relative to a plurality of "teeth' 31 on the element. The element 34 is provided with an aperture which permits the broach 20 to pass from the end of the gun barrel. The fluid forced into the chamber 25 also passesiromthe end of the gun barrel and through the-supporting element 34 where it engages a deflector 39 and flows into the bottom of the base H. The deflector 39 is connected by a link 42 to the head 34 and is moved out of the positionillustrated when the wheel 38 is operated to permit the removal of the broach. The deflector-39 will be moved into the position illus-. trated when the element 34 is moved into barrel engaging position. A suitable spring 4| may be employed to counteract the weight of the deflecting element.

In Fig. .6, the broach 20 is illustrated enlarged as being provided with a plurality of helical rows of teeth 43. The rows of teeth machine grooves in the inner surface of the gun barrel leaving lands disposed therebetween. The rear end of the bro'ach'is provided with a concave recess 44 for receiving the convex end 45 of the push rod 23. This arrangement provides a ball and socket connection which permits the broach to readily turn independent of the push rod 23.

..,The opposite end of broach 20 is provided with fingers. 41 which are bowed outwardly by springs 45 48. The end faces of the fingers 41 project outwardly sufficiently to engage the end of the broach receiving element 2 8 to prevent this end of the broachfrom being inserted therein, When the broach is pushed from the tube 28, the fingers 4! are collapsed so that they will move into the barrel. 1 After a barrel has been broached, the broach isremoved from the supporting element 34 which is then moved out of engagement with the barrel which is then removed. The broach is inserted in the broach receiving element 28 and a new barrel is secured to, the cap 32 andaccurately positioned by the element 34. The head 12 is then moved towards the chamber 19 causing the push rod23 to move the broach through the rifle barrel, During the broaching operation a coolant under pressure isdelivered to the chamber I9 and forced through the apertures in the tube 28.. The coolant flows over the broach and through the rifle barrel breaking oil the fine chips and washing them from the barrel out through the support 34 where it is directed by the deflector 39 into the base I I. In view of the ball and socket connection between the broach and push rod,.the broach 20 will turn following the lead of the helically disposed rows of teeth on the broach. In Fig. 8, I have illustrated-a section of the, broach to disclose the rows of teeth 43 and their relation to the grooves in the gun barrel, a section of which is illustrated in .Fig. 9.

The broach will produce like sections at all points,

provided :therein', and this; epistoniis mounted zon throughoutth'e length offthebarrel and will provide similar landsixand'groovesjn alllike gun barrels. v W ith respect to the formofsrtheinvention show-n byFiguresJIO to 13, inclusive, the'difference be.-

, tween-this arrangementmand that, previously described-resides principally 'inthe means for controlling and moving the push rod. Generally, coolant-"is introduced; along the broach and into the gun barrel in the samemanner; and for this reason this part :of .thearrangement' largely has been omitted in the drawings. .i

, Referring now particularlynfto 1,0, the

broach is-indicatedby thesamenumeral 2c, the aperturedtube around the-breach is indicated by the same .numer al'zfi; whilethe chamber casting for. the coolant, and which-corresponds to'the casting; l9; islindicated at .55. The. right. end of the-tube 28 -.is threaded intora head 5| tha't'is edforreciprocation ongu-idje 5'! ofthe base I! of i the machine.-ephis-cylinder, a's'shown by Figure 13," istransversely keyed, as indicated at 5 3, to a block 60, which'isadapted toreciprocate with the cylinder. The blocklia] :is longitudinally -apert-ured as indicatedatt l ,and this aperture receivesa pin 5 '62 which at its. leftend has a-relativelyshcrt. central opening 63 receiving the end of the push rod 52. At its left end, the:i'pinwiizuhasma head '54 disposed in alarger; opening fi5rinigthe left end of the block 69,-and this'headgengages a thrust bearing. 66 likewise disposed in-the opening 65. The opposite end of' the pin .62 has -a threaded portion? 61 for receivingya nut 68iandthe latter engagesga second thrust bearing disposed againstthe end of-the blocka, It will be appreelatedthat-this arrangement locks the pin 82 to the 'head-H5l,:aswill be readily the block *for axial movement therewith, while at the-samev time the pin can bereasi-lyturned about its own axis and with respectto the block. Beyond the threaded portion Elf-of the pin, the latter has an extension 'll Iwhich projects-z into an openingin aguide bar l2i- ?Thisi part' of the pin is-keyed to the guide-bar, asindicated at l3, and set screws lock the twotogether-against axial separation. -It .maybe mentioned here that the guide, bar 12 is provided with-spiralgrooves 1 5, which; engage ,-a ,similarly arranged; rib: T6; in

a stationary guide tube l1, sotha-t during recipro-' cation of the guide bar, it is turned. 1 From the foregoing, it .should-ibe' cleari that when the block 60 moves to the left-,vthe guide bar H and the 'pin will-turn and the turning may be synchronized with the natural turning of the broach occurring as the latter moves through the gun barrel. While the push rod might normally be turned by frictional contact at-its ends with I the breach and pin 62, it is preferred to positively lock the broach, rod and pin together so that For reciprocating the cylinder 56, a piston is a piston? rodrwhicrixcomprises an-inner; tube;-8;l

and anouter tuber-82 :thatsproject. to one end'iof the cylinder... Beyondcthe ends :of. the cylinder,

the tubes 8 l Land". 82. areriastened in asblock' 83 and are; connected respectively: tor: conduits. 84

and 85 .l eading,.thereto.z These conduits-extend to a. suitable :yalve,; -which,,;when:. operated: in one manner, causes zfluidwunder pressure .to fiow through-tone conduitzzand allow fluid to exhaust. from the other, and when ireversed in; operation causes the first; conduit toyzbeyiopenedi to exhaust .a'ndythe' second .-conduit-=.-toisbeztopenedxto fluid under. pressure. ;It.will:.be noted that the tube' 8| extends-t0 the left side of the piston and'isiopen tothis' side so that fluidinayzbe conductedtoand exhausted from-'thiscsidexof the piston gwhilethe tube-82 has alradialqopening 86 'allowingfluid to be goonductedto: and exhausted from the right side ofx the piston. "It should thus: beapparent that by i operation of the valve; fluid under pressure maybeconducted tq 0118251618 ofv the pistonor the other, depending' uponythe" valve operation, andthat fluid attheopposite side of the piston may be exhausted. Since-the piston and tubes are stationary; the" movement that will result'will be a, movement ofzthe cylinder 56. v All of the foregoing: relates towthe manner in which the push rod i s-moved" and themeans'for accomplishing this mov'ement. -Since the push rod, however, is small; inTdiameterpit is desirable to support it,..as.'previously explained, and the improved means for guiding and supporting the pushrod while permitting its turning will now be described. Y

Referring'to Figures: 10::and 11 particularly, castings. and 5.88, ,are;i;'niounted on the upp'er side of th'erb'ase'-al.il:,:andztheseare constructed and arrangedto providesaz-central, longitudinal passageway. 89,. andiwside passageways 90-and9l'.

These; passageways or chambers are open atboth ends of the. casting,:5and the central-passageway ga -receives the :upper part'of the block'60 so that the latter may reciprocate therein. A key 'plate cha n.e aeing --b1ock-94. :As best shown Icy-Fig:

ure 12, each of the chain e'riga'gingblocks-Sl has upper andlower legs 195xand '96; and a passagew Qfhbetween; such leg s;-:anduthese are adapted to cooperate withone of W b s cure,

; Referring to figures 12 and 13; each Cha1h60l1iprises pivot pins 98 assembled with anzup'per lih'e of links 9; and [901, rollers -I0| belo'wthe latter, a; line of-links l;0:2*,r-l03,5and lM-below the rollers l9 l1, r olle rs l 05---below .;links; l 04,": then 'a lineof ,lus, lege d moss-rollers 111a, and a line of links llfl and l ,r'rnemn-ers 'llll'and I09'have rolling contact with the legs and 96 of block 94 while the links I00 and I02 and the links I08 and H0, respectively embrace legs 95 and 96 and guide, as well as vertically support the chain. Roller l05is grooved peripherally, as indicated at l l2, and the grooves in the rollers I05 of both chains provide a cylindrical passageway or guideway for the push rod 52. It may be notedhere that cylindrical flanges H3 and H4 are provided on each roller'l05 at the sides of the .groove and that the rollers substantially contact through these flanges. l

I As shown by Figure 13, the end li k m;

the chains, as presently H1 straddle the'end of the block 60 and are connected thereto by means-of a pin H5. Thus, when the-block J60. is moving rearwardly, the chain devices are pulled along with it.

As best shown by Figures 10 and 11, the chains at the left end passi'over sprocket wheels I I6 and then 'rearwardly throughthe passageways 90 and 9|; At the.-rear: en'ds, the chains are connected to cables H'lthat pass overpulleys H8 and are connected to counter weights I I9. Thus, during forward'mo'vement of the block 60, the counter weights pullathechainalongwith the block and then upon rearward-.movement of the block 60, the block'itself pulls the chains and raises the counter weights." From the foregoing descriptionit will be apparent'that. the arrangement shown by Figures :10 to."13 provides a moving guideway for the push rod which is in the form of chains that travel -with' the' rodand thereby eliminate any sliding friction duringthe broaching operation. Moreover, this guideway permitsturning of the push rod without appreciable friction. Again it is-apparent' that thearrangement provides a means for positively turning the'push rod in synchronism with the turning of the broach and for turning of the push rod and broach positively.

While I haves-described and illustrated more than-one embodiment of my invention, it Will be apparent to those skilled in the art that various changes, omissions, additions, and substitutions maybemade therein without departing from the spiritqandscopeof my invention, as set forth in the following claims;

What is claimed is:'

, 1.; Amachine for'cuttinghelical grooves in a tubular element, including, in combination, a push rod,a support for a broach aligned therewith, a broach having an abutting engagement only with said push rod, a projecting finger on HIEOIIBI end'of the broach which prevents its wrong disposition on the work support, and means for supporting a workpiece aligned with said broach=.;

' '2. A breaching machine including, in combina- Y ing said rod, and means including grooved rollers for guiding and supporting the push rod as it is advanced: x

-4; A- machine for advancing a cutting tool through a tubular member,'comprising a push rod for so advancing thetool means for pushing saidrod, .andmeans including chains engaging opposite sidesof thepush rod for guiding'and supportingithe push rod as it is being pushed. 5. A machine for advancing a cutting tool through a tubular member, comprising a push rod for so advancing the tool means for pushing said rod, and means including chains having grooved rollers engaging opposite sides of the pushrod for guiding and supporting the push rod as it is being pushed.

6. A machine for advancing a cutting tool through a tubular member, comprising a push rod for so advancing the tool, means engaging the rod for advancing it into the member, flexible devices movable with said means and engaging opposite sides of the push rod between said means and the tubular member for guiding and supporting the rod, and means for allowing portions of said devices to progressively move away from the rod as said means approaches the tubular member so as to compensate for the decrease in length of push rod projecting from the tubular member.

'7. A machine for advancing a cutting tool through a tubular member, comprising a push rod for so advancing the tool, means engaging the rod for advancing it into the member, flex ible devices movable with said means and engaging opposite sides of the push rod between said means and the tubular member for guiding and supporting the rod, and'means' for allowing portions of said devices to progressively move away from the rod as said means. approaches the tubular member so as to compensate for the decrease'in length of push rod projecting from the tubular member, said flexible devices comprising chains on oposite sides of the push rod.

8. In a machine for breaching spiral grooves in the interior of a cylindrical member, a support for the member to be broached, aclosed broach receiving chamber in communication with one end of said cylindrical member when the latter is mounted in said support, means to advance a broach on its cutting stroke from a position within said chamber through said cylindrical member from said one end of the cylindrical member to'the other, and means for supplying fluid under pressure to said chamber to fill the chamber and cause a flow of fluid in the direction of movement of the broach through the cylindrical member during the cutting stroke.

9. ma machine for broaching rifle grooves in a gun barrel, a closed chamber adopted to receive a broach and having an opening at one end, means for supporting a gun barrel with one end in communication with said opening, means to advance a rifling broach on its cutting stroke from a position within said chamber through said barrel, and means for supplying fluid under pres sure to said chamber to flll the chamber and cause a flow of fluid through the barrel in the direction of movement of the broach during the cutting stroke.

RICHARD A. THOMPSON. 

